Mr. Donalds brings up some valid issues here in his reply.
Usually the looser an engine is the faster it goes, but oil consumption
at speed will be excessive.
There are several trains of thought on a new engine break in, and  this
can be debated till the cows come home.
One thought is; break it in fast, it'll burnish in the rings and be a
fast engine.
Break it it slow, it'll carbon up the ring lands, and be a slow engine.
I drive a new engine ( or rebuilt) at normal highway speeds, and haven't
experienced any premature failures.
Now Mr. Donalds mentions upper end lubrication and valve and seat
failures at higher speeds.
This is absolutely correct.
If one was smart and knew he was going on a long trip for long durations
of highway speeds ( and then some) he would be wise and add some sort of
upper end lubrication measures in the fuel to combat this accepted, and
common  problem.
I do in my Vanagon.
I do in the Queens vehicles.
I do in the made in the US of A vehicles
No valve seat recession or burning, no rings collapsing
No burnt valves.
It works well, and is a simple combative,  preventative maintenance
measure.

Oh, and an accessory oil cooler works well also to keep the overall oil
temps down to keep the oil's viscosity at the same level as when it was
put in the engine.
Another good idea for high speed traveler's.

RC